Preparation of suspensions of watersoluble solids in oleaginous media



3,065,175 Patented Nov. 20, 1962 3,065,175 PREPARATIGN F SUSPENSHONS 0F WATER- SOLUBLE SQLIDS EN OLEAGMGUS MEDEA Edward John Blake and Walter Morrison, Sanitary-on- Thames, England, assignors to The British Petroleum Company Limited, London, England, a joint-stock corporation of Great Britain No Drawing. Filed 6st. 26, 195?, Ser. No. 848,533

Claims priority, appiication Great Britain (Pet. 31, 1958 17 Claims. (Cl. 252-18) This invention relates to the preparation of suspensions of water-soluble solids in oleaginous media, such as hydrocarbons, in which the solids are insoluble.

It is often desired to incorporate water-soluble, oilinsoluble solids in oleaginous media, such as mineral lubricating oils and greases. For example, sodium nitrite at about 2% weight concentration is now frequently used as a corrosion inhibitor in lubricating grease. To be elfective as a corrosion inhibitor and to eliminate any abrasive tendencies, the crystals of the sodium nitrite must be stably dispersed and of very small particle size, preferably less than microns. The same considerations also often apply to dispersions of other water-soluble solids in other oleaginous media.

One method of obtaining a stable suspension of finely divided particles is to use large amounts of petroleum sulphonates as dispersing agents but it has been stated that the compositions produced are very sensitive to the presence of water and, in the case of greases, tend to lose their structure.

Another method which has recently been proposed for this purpose is to emulsify an aqueous solution of the solid with an oleaginous liquid to form a water-in-oil emulsion using an emulsifying agent capable of forming such an emulsion, and thereafter heating the emulsion to drive off the water. However, when using the emulsifying agents suggested for this technique, e.g. sodium stearate, sodium hydroxystearate, basic calcium alkyl sulphonates and sodium alkyl sulphonate, poor dispersions with large individual crystal sizes were obtained.

We have now found that improved suspensions can be obtained by using a particular material as an emulsifying and dispersing agent.

According to the invention, there is provided a method of preparing a suspension of particles of a water-soluble solid in an oleaginous medium, in which an aqueous solution of the solid is emulsified with an oleaginous liquid to form a water-in-oil emulsion using a vegetable wax as an emulsifying agent, and the emulsion is thereafter dehydrated.

The vegetable wax should preferably be one, the saponification value of which (as measured by IP 136/58) is at least 10, preferably at least 30 units greater than the acid value (as measured by IP 139/57).

Examples of suitable vegetable Waxes which may be used are: carnauba wax, candelilla wax, esparto wax, fiax wax and ouricury Wax.

In carrying out the method of the invention, the vegetable wax may conveniently be dissolved in the oleaginous liquid and the aqueous solution thereafter added. The emulsion may be produced by agitation of the mixture, e.g. by stirring, milling or both. Dehydration of the emulsion may be most conveniently effected by heating, eg at a temperature of 115 l70 C. During dehydration by heating it'is advisable to continue stirring the emulsion to reduce foaming and to ensure that the emulsion does notbreak.

The oleaginous liquid may be a mineral oil, e.g. a lubricating oil, a residue, a fuel oil or kerosin. It may also be a vegetable oil, e.g. castor oil, or a synthetic oil,

e.g. a diester, a polyglycol, a polyether, or a siliconcontaining synthetic oil. In order to produce a lubricating grease containing a dispersion of a water-soluble solid, a dispersion of the solid in lubricating oil prepared as described above may be either mixed with a grease or thickened to a grease consistency in known manner with a grease-forming agent.

Preferably the concentration of water-soluble solid in the final composition is 0.525% by weight.

Preferably the amount of vegetable wax used is 0:1- l0%, especially 0.5-7.5 by weight on the oleaginous liquid.

in general it is desirable to use a fairly concentrated solution of the water-soluble solid as this reduces the amount of water which has to be removed from the emulsion. Solutions having a solids concentration of 2070% wt. are particularly satisfactory.

Water soluble solids which can be suspended in oleaginous media by the method according to the invention include water-soluble corrosion inhibitors such as alkali metal and ammonium nitrites, carbonates, bicarbonates, sulphites, borates, chlorates, perchlorates, hypochlorites, silicates, phosphates, salicylates, citrates, tannates, lactates, tartrates, oxalates, phthalates, acetates, iodaates, arsenites, chromates, molybdates and tungstates, and amine nitrites, phosphates and iodates. However, the invention is not limited to the use of water-soluble solids that are corrosion inhibitors. Examples of other water-soluble solids that may be used include water-soluble extreme pressure agents such as hydroxy fatty acids, polycarboxylic acids, hydroxy polycarboxylic acids, organic salts (e.g. sodium benzoate), amides and amino acids.

A number of examples of the invention will now be described. The vegetable waxes used in the examples had the properties shown in Table I.

TABLE I Oar- Oande- Ex- Ouri- Flax nauba lilla part0 cury Wax Wax Wax Wax Wax Colour Dark Light Middle Middle Middle Brown Brown Brown Brown Brown Normal texture atroom temperature Hard Hard Hard Hard Hard and and and an and Brittle Brittle Brittle Brittle Brittle Melting point (IP 133) C- 84. 1 71. 1 83. 5 84. 8 74 Congealing point (IP 78) C 77.8 67.8 70 71. 1 Acid Value (IP 139/57) mg.

KOH 6 11 20 8 14 Saponitication Value (IP 126 58) mg. KOH/g 88 68 67 77 Example 1 Two and a half grams of carnauba wax were dissolved in grams of 150/75 grade lubricating oil (Redwood I viscosity at F.: seconds; viscosity index: 75) by warming and gentle stirring. Fifteen grams of sodium nitrite crystals were dissolved in 30 grams of distilled water and this solution was emulsified with the oil/wax solution using a laboratory mixer operating at 3000 revolutions per minute. The water-in-oil emulsion so formed was then heated to 140 C. to drive otf the water while high speed stirring was continued. (Heating to 140 C. took approximately 15 minutes and the dispersion was held at slightly over 140 C. for 1-2 minutes.) The mix was then allowed to cool to atmospheric temperature with gentle stirring.

On examining the anhydrous dispersion of sodium nitrite crystals in oil so formed, under the microscope using polarised light, it was found that a fine even dispersion of sodium nitrite crystals had been obtained, no individual crystal size being greater than microns.

This experiment was repeated using in turn the other waxes listed in Table I and in each case good dispersions were obtained, no individual crystal size being greater than 5 microns.

The experiment was again repeated using, in turn, potassium chromate, sodium benzoate and sodium tungstate in place of sodium nitrite and using candelilla wax as the emulsifying agent. Again, fine even dispersions were obtained, no crystal size being greater than 5 microns.

Example 2 grams of carnauba wax were dissolved in 500 grams of 150/75 grade lubricating oil. 75 grams of sodium nitrite were dissolved in 150 grams of distilled water and the oil and aqueous solution emulsified by high speed stirring using a laboratory stirrer, followed by milling between Carborundum stones set at 0.001 inch clearance and rotating at 3000 revolutions per minute. The emulsion was then dehydrated by heating to 140 C. with high speed stirring. (Heating time to 140 C. was approximately 30 minutes. The material was held at 140 C. for 1-2 minutes.) A fine dispersion of sodium nitrite was obtained in which individual size was less than five microns.

A batch of lithium base grease was then made in known manner from:

405 grams hardened (hydrogenated) castor oil, 57 grams lithium hydroxide monohydrate, and 2038 grams mineral lubricating oil (150/75 grade).

Penetration at 25 C.worked: 60 strokes (IP 50/56) 251 mm./10. Penetration at 25 C.-worked: 100,000

strokes (IP 50/56) 285 mm./10. Drop point (IP 31) 185 C. Oil separation on storage at 25 C. (IP

121/57) 0.2% wt. Bleed test (DTD 825A) 1.7% wt.

Penetration at 25 C. after 4 hours in Shell Roll tester at room temperature (SMS 466) 245 mm./10. Penetration at 25 C. after 4 hours in Shell Roll tester at 100 C. (SMS 466) 308 mm./10. NaNO particle size Less than 5 Corrosion test No rusting observed.

No difficulties were experienced in pumping the grease through a 200 mesh BSS sieve and no agglomeration or crystal growth was observed in the grease after two months storage.

Example 3 By way of comparison, a lithium base grease was made in the same manner as in Example 2 using the following ingredients:

Mineral lubricating oil (as used in Example 2) 85.2% wt. Hardened castor oil 13.0% wt. Lithium hydroxide monohydrate 1.8% wt.

No sodium nitrite was added. Inspection data were as follows:

Penetration at 25 C.-worked:

60 strokes (IP 50/56) 238 mm./10.

Penetration at 25 C.-worked:

100,000 strokes (IP /56) 289 rum/10. Penetration at 25 C. :after 4 hours in Shell Roll tester at room temperature (SMS 466) 25 1 mm./ 10. Penetration at 25 C. after 4 hours in Shell Roll tester at 100 C. (SMS 466) 366 mm./10. Drop point (IP 31) 189 C. Oil separation on storage at 25 C. (IP 121/57) 2.4% wt. Bleed test (DTD 825A) 3.9% wt. Corroision test Severe rusting on all bearing parts.

It appears from the above data that the presence of sodium nitrite in a lithium grease may cause a slight lowering of drop point but this is not significant in terms of rig performance and the drop point of the grease of Example 2 is as good as the drop points of currently marketed lithium greases containing sodium nitrite.

The mill used in the above examples was a Premier colloid paste mill. This is a high speed mill (3000 revolutions per minute) in which the material to be milled is fed between a 5 inch Carborundum rotor and a Carborundum stator, the annular gap being variable up to 0.025 inch.

The corrosion test was carried out in a rig consisting essentially of a 35 millimetre bore, double row, selfaligning ball race fitted with a pressed steel cage and housed in a plummer block. It was operated at 80 revolutions per minute and with no load applied.

The bearing is filled with the grease under test and the housing is packed in such a Way as to form a cup round the bearing, 20 millilitres of water are introduced into this cup.

The rig is run (with water present) on 3 consecutive days for 8 hours each day followed by a 3-4 day static period. At the end of this static period the bearing parts are examined for rusting and corrosion.

The use of vegetable waxes in producing the dispersions according to the invention has the following advantages:

(a) They are readily available and relatively cheap. No elaborate processing or extraction procedures are required for its production.

(b) Greases produced in the manner described above using candelilla wax are not darkened in colour. The other waxes listed produce a darker coloured solid/oil dispersion which causes some darkening of the grease colour to produce a milk chocolate or coffee effect. Thus the dispersants may be chosen to produce dark or light coloured greases as desired.

(0) It is not necessary to use evaporation on heated drums or recirculation through fine nozzles during the dehydration step as mentioned in previous proposals for producing dispersions by the emulsification technique.

(d) Satisfactory corrosion-inhibited greases may be made using conventional and established grease making equipment, i.e. mills used for grease production and normal open grease kettles.

We claim:

1. A method of preparing a suspension of particles of a water-soluble solid in an oleaginous medium which comprises emulsifying an aqueous solution of the solid with an oleaginous liquid and a vegetable wax to form a water-in-oil emulsion, and thereafter dehydrating the emulsion.

2. A method according to claim 1, in which the vegetable wax in one selected from the group consisting of carnauba wax, candelilla wax, esparto wax, flax wax and ouricury wax.

3. A method according to claim 1, in which the vegetable wax has a saponification value of at least 10 units greater than its acid value.

4. A method according to claim 3, in which the vegetable wax has a saponification value of at least 30 units greater than its acid value.

5. A method according to claim 1, in which the vegetable wax is dissolved in the oleaginous liquid and the aqueous solution thereafter added.

6. A method according to claim 1, in which the emulsion is produced by agitating the oleaginous and aqueous phases.

7. A method according to claim 1, in which the dehydration of the emulsion is efiected by heating.

8. A method according to claim 7, in which the heating is carried out at a temperature of 115-170 C.

9. A method according to claim 1, in which the oleaginous liquid is a lubricating oil.

10. A method according to claim 9, in which the lubricating oil is a mineral lubricating oil.

11. A method according to claim 1, in which the amount of vegetable wax used is 01-10% by weight of the oleaginous liquid.

12. A method according to claim 11, in which the 20 amount of vegetable wax used is 0.5-7.5 by weight of the oleaginous liquid.

13. A method according to claim 1, in which the aqueous solution has a solids concentration of 20-70% by weight.

14. A method according to claim 1, in which the concentration of water-soluble solid suspended in the final composition is 05-25% by weight.

15. A method according to claim 1, in which the water-soluble solid is sodium nitrite.

16. In a method of producing a lubricating grease containing a suspension of particles of a water-soluble solid, the improvement which comprises preparing a suspension of particles of the water-soluble solid in a lubricating oil in a manner as specified in claim 9, and mixing the resulting suspension with a grease.

17. In a method of producing a lubricating grease containing a suspension of particles of water-soluble solid, the improvement which comprises preparing a suspension of particles of the water-soluble solid in a lubricating oil in a manner as specified in claim 9, and thickening the resulting suspension to a grease consistency with a greaseforming agent.

References Cited in the file of this patent UNITED STATES PATENTS 2,235,161 Morway et al Mar. 18, 1941 2,342,199 Hurtt Feb. 22, 1944 2,758,085 Oberright Aug. 7, 1956 2,921,899 Sproule et al Jan. 19, 1960 FOREIGN PATENTS 778,822 Great Britain July 10, 1957 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3 O65 175 November 20 1962 Edward John Blake et all It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below. i

Column 2, TABLE I first column line 5 thereof for "(IP 78) Y read (IP 76) same TABLE I i first column lines 8 and 9 thereof v for "(IP 126 58) read (IP 136/58) same TABLE I third column line 6 thereof n for "719 1" read 71,? -g column 4 line l3 for "Corroision" read Corrosion Signed and sealed this 18th day of June 1963 (SEAL) Attest:

ERNEST w. SWIDER DAVID D Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 065 175 November 2O 1962 Edward John Blake et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2,, TABLE I first column line 5 thereof for "(IP 78)? read (IP 76) same TABLE I first column lines 8 and 9 thereof for "(IP 126 58) read (IP 136/58) same TABLE I third columm line 6 thereof 9 for "7101" read 71,7 column 4 line 13 for "Corroision" read Corrosion Signed and sealed this 18th day of June 1963c.

(SEAL) Attest:

ERNEST w. SWIDER. DAVID D Attesting Officer Commissioner of Patents 

1. A METHOD OF PREPARING A SUSPENSION OF PARTICLES OF A WATER-SOLUBLE SOLID IN AN OLEAGINOUS MEDIUM WHICH COMPRISES EMULSIFYING AN AQUEOUS SOLUTION OF THE SOLID WITH AN OLEAGINOUS LIQUID AND A VEGETABLE WAX TO FORM A WATER-IN-OIL EMULSION, AND THEREAFTER DEHYDRATING THE EMULSION.
 9. A METHOD ACCORDING TO CLAIM 1, IN WHICH THE OLEAGINOUS LIQUID IS A LUBRICATING OIL.
 16. IN THE METHOD OF PRODUCING A LUBRICATING GREASE CONTAINING A SUSPENSION OF PARTICULES OF A WATER-SOLUBLE SOLID, THE IMPROVEMENT WHICH COMPRISES PREPARING A SUSPENSION OF PARTICLES OF THE WATER-SOLUBLE SOLID IN A LUBRICATING OIL IN A MANNER AS SPECIFIED IN CLAIM, 9, AND MIXING THE RESULTING SUSPENSION WITH A GREASE. 